Optical member and optical product provided therewith

ABSTRACT

An optical member comprising a polymer which is amorphous and has a glass transition temperature of not lower than 110° C. and optical property parameters O′ R (∞)) and O′ G (∞) that satisfy the following inequality (1),
 
| O′   G (∞)|&lt;− 0.75×|   O′   R (∞)|+ 0.017   (1), 
 
is superior in its heat resistance and transparency and high in its stability of optical properties. Therefore, the optical member can be used as, for example, a constituent of optical systems in a liquid crystal display, thereby suppressing change in a display color tone depending on variation of using circumstances of the liquid crystal display.

TECHNICAL FIELD

The present invention relates to an optical member suitably applicableto optical products such as liquid crystal displays and an opticalproduct provided with said optical member.

BACKGROUND ART

In recent years, various plastic materials having opticalcharacteristics such as high transparency have been used for lenses suchas lenses for eyeglasses, f·θ lenses and pick up lenses, prisms, opticalfibers, disk substrates for an optical recording medium or amagneto-optical recording medium, and constituents of a liquid crystaldisplays. It is important for plastic materials, particularly, thoseused as a material for a constituent of optical systems in a liquidcrystal display provided with a carrying plate, a polarizing plate, asubstrate of liquid crystal cells, a light diffusion plate and acondensing film, to be transparent as well as superior in theirproperties to polarization and their heat resistance. However, plasticmaterials now used for a constituent of optical systems in an opticalproduct are not sufficient in their properties to polarization. Forexample, a liquid crystal display comprising a part of a conventionalplastic material as the optical systems frequently results in change ina display color tone depending upon variation of using circumstancessuch as a temperature variation and a humidity variation.

PROBLEM TO BE SOLVED BY THE INVENTION

Under these circumstances, an object of the present invention is toprovide an optical member superior in its optical properties and heatresistance. Another object of the present invention is to provide anoptical member capable of suppressing change in display color tone whenused, for example, as a constituent of optical systems or as a partthereof in a liquid crystal display.

DISCLOSURE OF INVENTION

The present inventors have extensively studied, and as a result, it hasbeen found that a polymer having specific values of optical propertyparameters, O′R(∞) and O′G(∞), is suitable as a material for an opticalmember, and by using it, the above-described problems can be solved.Further, it has been found that the above-described polymer particularlysuitable as a material for an optical member is composed of plural kindsof monomer units having specific polarization independently. The presentinventors have accomplished the present invention based on theabove-described findings.

That is, the above-described problems can be solved by the followingmeans [1] to [11].

[1] An optical member comprising a polymer which is amorphous and has aglass transition temperature of not lower than 110° C. and opticalproperty parameters O′_(R)(∞) and O′_(G)(∞) that satisfy the followinginequality (1),|O′_(G)(∞)′<−0.75×|O′_(R)(∞)|+0.017  (1).[2] The optical member according to the foregoing item [1], wherein thepolymer comprises a copolymer comprising an m kind of monomer unitsatisfying the following inequality (2), wherein m is an integer of notless than 1, and an n kind of monomer unit not satisfying the followinginequality (2), wherein n is an integer of not less than 1, andsatisfying the following inequalities (3) and (4),−9.5×10⁻²⁵ cm³<Δα_(R) ^(S)  (2)−1.0×10⁻²⁴<Δα_(R) ^(P)<−5.0×10⁻²⁵ cm³  (3)3.4×10⁻²⁵<Δα_(G) ^(P)<5.4×10⁻²⁵ cm³  (4)wherein, in inequality (2), Δα_(R) ^(S) is a parameter defined by thefollowing equality (I),Δα_(R) ^(S)=α₁ ^(S)−(1/2)(α₂ ^(S)+α₃ ^(S))−(3/4)P(α₁ ^(S)−α₃ ^(S))  (I)wherein, in equality (I), α₁ ^(S), α₂ ^(S) and α₃ ^(S) are each a mainvalue of polarizability tensor of a side chain in a monomer unit andsatisfy a relation of α₂ ^(S)≧α₁ ^(S)≧α₃ ^(S), and P is 0 when themonomer unit has a side chain bonding to main chain at two or morepositions, or P is 1 when the monomer unit has no side chain bonding tomain chain at two or more positions,and wherein, in inequalities (3) and (4), Δα_(R) ^(P) and Δα_(G) ^(P)are parameters defined by the following equalities (i) and (ii),respectively, $\begin{matrix}{{\Delta\quad\alpha_{R}^{P}} = {{\sum\limits_{i = 1}^{m}\left( {X_{i}\Delta\quad\alpha_{RAi}^{S}} \right)} + {\sum\limits_{j = 1}^{n}\left( {Y_{j}\Delta\quad\alpha_{RBj}^{S}} \right)}}} & (i) \\{{\Delta\quad\alpha_{G}^{P}} = {{\sum\limits_{i = 1}^{m}\left( {X_{i}\Delta\quad\alpha_{GAi}^{S}} \right)} + {\sum\limits_{j = 1}^{n}\left( {Y_{j}\Delta\quad\alpha_{GBj}^{S}} \right)}}} & ({ii})\end{matrix}$wherein, in equalities (i) and (ii), X_(i) is a molar fraction of anarbitrary monomer unit satisfying inequality (2), Y_(j) is a molarfraction of an arbitrary monomer unit not satisfying inequality (2),Δα_(RAi) ^(S) is Δα_(R) ^(S) of an arbitrary monomer unit satisfyinginequality (2), Δα_(RBi) ^(S) is Δα_(R) ^(S) of an arbitrary monomerunit not satisfying inequality (2), and, in equality (ii), Δα_(GAi) ^(S)and Δα_(GBi) ^(S) are Δα_(G) ^(S) value defined by the followingequality (II) with respect to an arbitrary monomer unit satisfyinginequality (2) and Δα_(G) ^(S) value defined by the following equality(II) with respect to an arbitrary monomer unit not satisfying inequality(2), respectively,Δα_(G) ^(S)=(1/4)(α₂ ^(S)−α₃ ^(S))−(1/8)P(α₁ ^(S)−α₃ ^(S))  (II)wherein, in equality (II), α₁ ^(S), α₂ ^(S), α₃ ^(S) and P are asdefined above.[3] The optical member according to the foregoing item [2], wherein thecopolymer comprises a monomer unit derived from a compound selected fromthe group consisting of olefins having 2 or 3 carbon atoms, norborneneand norbornene derivatives as the monomer unit satisfying inequality(2), and a monomer unit derived from a vinyl group-containing cycliccompound as the monomer unit not satisfying inequality (2).[4] The optical member according to the foregoing item [3], wherein thecopolymer comprises a monomer unit derived from an aromatic vinylcompound as the monomer unit not satisfying inequality (2).[5] The optical member according to the foregoing item [4], wherein thecopolymer has a total molar fraction of the monomer unit not satisfyinginequality (2) ranging from 0.1 to 0.4 inclusive.[6] The optical member according to the foregoing item [3], wherein thecopolymer comprises a monomer unit derived from an alicyclic vinylcompound as the monomer unit not satisfying inequality (2).[7] The optical member according to the foregoing item [6], wherein thecopolymer has a total molar fraction of the monomer unit not satisfyinginequality (2) ranging from 0.3 to 0.8 inclusive.[8] The optical member according to any one of the foregoing items [1]to [7], which is a polarizing plate-protecting film.[9] The optical member according to any one of the foregoing items [1]to [7], which is a substrate for liquid crystal cells.[10] A polarizing plate, wherein the optical member according to any oneof the foregoing items [1] to [7], which is a polarizingplate-protecting film, is mounted on at least one side surface of apolarizing film.[11] A liquid crystal display, which is provided with a substrate ofliquid crystal cells according to the foregoing item [9] and/or apolarizing plate according to the foregoing item [10].

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a graph showing O′_(R)(∞) and O′_(G)(C) of the polymersobtained in Examples 1 to 3 and Comparative Examples 1 to 5.

FIG. 2 is a graph showing Δα_(R) ^(P) and Δα_(G) ^(P) calculated fromthe monomer units constituting the polymers obtained in Examples 1 to 3and Comparative Examples 1 to 5.

BEST MODE FOR CARRYING OUT THE INVENTION

In the present invention, the term “optical member” means a memberhaving an optical function. The optical member is not particularlylimited in its size, its shape and its existing state. The opticalmember in accordance with the present invention can be (1) one existingby itself independently, (2) one integrally formed with other parts bymeans of laminating or the like, or (3) one combined with other parts bymeans of supporting or fixing in an appropriate manner to constitute anapparatus. Examples of the optical member in the state of (1) includelenses, prisms, optical fibers, disk substrates for an optical recordingmedium or a magneto-optical recording medium, which are now stored ordistributed to be used as a part for an apparatus; polarizingplate-protecting films, which are awaiting lamination with a polarizingfilm for polarizing plate use, and substrates for liquid cells to beused for a liquid crystal display. Examples of the optical member in thestate of (2) include polarizing plate-protecting films constituting apolarizing plate through lamination with a polarizing film and liquidcell substrates, which have been used for a liquid crystal display.Examples of the optical member in the state of (3) include lenses of apair of spectacles that have been furnished with a flame, fez lensesthat have been incorporated in a laser printer, and pick up lenses thathave been incorporated in a CD player and a DVD player.

The optical member in accordance with the present invention comprises apolymer which is amorphous and has a glass transition temperature of notlower than 110° C. and optical property parameters O′R(∞) and O′G(∞)that satisfy the following inequality (1) The polymer is superior in itsheat resistance, because its glass transition temperature is not lowerthan 110° C. Further it is superior in its transparency, because it isamorphous. It has superior optical properties, because its opticalproperty parameters, O′_(R)(∞) and O′_(G)(∞), satisfy the followinginequality (1).|O′_(G)(∞)|<−0.75×|O′ _(R)(∞)|+0.017  (1)

The O′_(R)(∞) and O′_(G)(∞) in the present invention are parametersshowing optical properties of a polymer, and defined as follows.

<Definition of O′_(R)(∞) and O′_(G)(∞)>

The O′_(R)(∞) and O′_(G)(∞) of a polymer are defined according to a ruleof corrected stress optics (See T. Inoue et al. “Polymer”, 38, 1215,1997; T. Inoue et al. “Rheologica Acta”, 36, 239, 1997; T. Inoue et al.“Macromolecules”, 29, 6240, 1996; T. Inoue et al. “Macromolecules”, 24,5670, 1991; and T. Inoue et al. “KOBUNSHI RONBUN-SHU (a collection ofpapers on high molecules)”, 53, 602, 1996).

When vibration distortion ε*(ω), which is defined by an equality,ε*(ω)=ε₀ cos ωt, wherein ε₀ is an amplitude of distortion, ω is anangular frequency and t is time, is applied to a polymer, the stressσ*(ω) generated therefrom is expressed by an equality, σ*(ω)=σ₀ Cos(ωt+δ), wherein σ₀ is an amplitude of stress, ω and t are as definedabove, and δ is phase difference. And complex distortion modulus E*(ω)of said polymer is defined by an equality, E*(ω)=σ*(ω)/ε*(ω)=E′(ω)+iE″(ω), wherein E′(ω) is dynamic modulus, i is a unit of an imaginarynumber, and E″ (ω) is loss modulus. Similarly, a complex distortionoptical ratio of the polymer O*(ω) to double refraction Δn*(ω), which issimultaneously observed when the above-mentioned vibration distortion isapplied to the polymer and is defined by an equality, Δn*(ω)=Δn₀ cos(ω_(t)+δ_(B)), wherein Δn₀ is inherent double refractive index and δ_(B)is phase difference, is defined by an equality,O*(ω)=Δn*(ω)/ε*(ω)=O′(ω)+iO″(ω), wherein O′(ω) is a real number portionof the complex distortion optical ratio and 0″(ω) is an imaginary numberportion thereof.

According to the rule of corrected stress optics, the stress and doublerefraction of the polymer are described to be the sum of two components,R and G, and the following equalities hold.E′(ω)=E′ _(R)(ω)+E′ _(G)(ω)  (a)O′(ω)=O′ _(R)(ω)+O′ _(G)(ω)=C _(R) E′ _(R)(ω)+C _(G) E′ _(G)(ω)  (b)E″ (ω)=E″ _(R)(ω)+E″ _(G)(ω)  (c)O″(ω)=O″ _(R)(ω)+O″ _(G)(ω)=C _(R) E″ _(R)(ω)+C _(G) E′ _(G)(ω)  (d)

Herein, C_(R) and C_(G) are constants inherent to respective polymers.According to the rule of corrected stress optics, the R and G componentscorrespond to an orientation of a main chain of the polymer and anorientation of portions of the polymer other than the main chain,respectively.

Respective limiting values, O′R(ω) and O′_(G) (∞), at high frequencylimits of respective R and G components in the optical propertyparameter O′(∞) of the polymer expressed by the above equality (b) areexpressed by the following equalities.O′ _(R)(∞)=C _(R) E′ _(R)(∞)  (e)O′ _(G)(∞)=C _(G) E′ _(G)(∞)  (f)

According to the rule of corrected stress optics, the O′_(R)(∞) is aparameter related with an inherent double refractive index Δn₀ as in thefollowing equality.Δn ₀=(5/3)×O′ _(R)(∞)  (g)

The O′_(R)(∞) and O′_(G)(∞) can be determined in a manner describedbelow.

Vibration distortion periodically varying with the lapse of time isapplied to the polymer, and the generated changes in stress and doublerefraction are simultaneously measured. Based on the results andaccording to the rule of corrected stress optics, C_(R), C_(G),E′_(R)(∞) and E′_(G)(∞) are determined, and the obtained values aresubstituted for the equalities (e) and (f), thereby determining theO′_(R)(∞) and O′_(G)(∞).

The magnitude of the O′_(R)(∞) and O′_(G)(∞) of the polymer shows adegree of optical distortion of the polymer. When the O′_(R)(∞) andO′_(G)(∞) satisfy inequality (1), the polymer is suitable as a materialof the optical member. For example, when such a polymer is used as aconstituent of optical systems in a liquid crystal display, change in adisplay color tone accompanied with variation of using circumstances canbe suppressed to a satisfactory degree. From a viewpoint of suppressioneffect to change in a display color tone when the optical member isapplied, for example, for optical systems in a liquid crystal display,it is more preferred that the O′_(R)(∞) and O′_(G)(∞) of the polymerconstituting the optical member in accordance with the present inventionsatisfy the following inequality (1-2), and it is particularly preferredthat the O′_(R)(∞) and O′_(G)(∞) satisfy the following inequality (1-3).|O′ _(G)(∞)|<−0.37×|O′ _(R)(∞)|+0.0083  (1-2)|O′ _(G)(∞)|<−0.43×|O′ _(R)(∞)|+0.0083  (1-3)

From a viewpoint of optical properties, it is preferred that the polymerconstituting the optical member in accordance with the presentinvention, whose optical property parameters, O′_(R)(∞) and O′_(G)(∞),satisfy inequality (1), comprises a copolymer comprising an m kind (m isan integer of not less than 1) of a monomer unit satisfying thefollowing inequality (2) (hereinafter referred to as MU 1) and an n kind(n is an integer of not less than 1) of a monomer unit not satisfyingthe following inequality (2) (hereinafter referred to as MU 2).−9.5×10⁻²⁵ cm³<Δα_(R) ^(S)  (2)

In inequality (2), Δα_(R) ^(S), which means polarization of a side chainof the polymer, is a parameter defined by the following equality (I).Δα_(R) ^(S)=α₁ ^(S)(1/2)(α₂ ^(S)+α₃ ^(S))−(3/4)P(α₁ ^(S)−α₃ ^(S))  (I)

In equality (I), α₁ ^(S), α₂ ^(S) and α₃ ^(S) are each a main value ofpolarizability tensor of a side chain in a monomer unit and satisfy arelation of α₂ ^(S)≧α_(i) ^(S)≧α₃ ^(S), and P is 0 when the monomer unithas a side chain bonding to main chain at two or more positions, or P is1 when the monomer unit has no side chain bonding to main chain at twoor more positions. In other words, P is a parameter showing the presenceor absence of restriction to the side chain in the monomer unit by themain chain.

Further, it is particularly preferred that the polymer satisfying theforegoing inequality (1) is a copolymer which comprises the monomer unitsatisfying the above inequality (2) and the monomer unit not satisfyingthe above inequality (2), and moreover, is a copolymer which satisfiesthe following inequalities (3) and (4).−1.0×10⁻²⁴<Δα_(R) ^(P)<−5.0×10⁻²⁵ cm³  (3)3.4×10⁻²⁵<Δα_(G) ^(P)<5.4×10⁻²⁵ cm³  (4)

In inequalities (3) and (4), Δα_(R) ^(P) and Δα_(G) ^(P) are parametersdefined by the following equalities (i) and (ii), respectively.$\begin{matrix}{{\Delta\quad\alpha_{R}^{P}} = {{\sum\limits_{i = 1}^{m}\left( {X_{i}\Delta\quad\alpha_{RAi}^{S}} \right)} + {\sum\limits_{j = 1}^{n}\left( {Y_{j}\Delta\quad\alpha_{RBj}^{S}} \right)}}} & (i) \\{{\Delta\quad\alpha_{G}^{P}} = {{\sum\limits_{i = 1}^{m}\left( {X_{i}\Delta\quad\alpha_{GAi}^{S}} \right)} + {\sum\limits_{j = 1}^{n}\left( {Y_{j}\Delta\quad\alpha_{GBj}^{S}} \right)}}} & ({ii})\end{matrix}$

In equalities (i) and (ii), X_(i) is a molar fraction of an arbitrarymonomer unit satisfying inequality (2) Y_(j) is a molar fraction of anarbitrary monomer unit not satisfying inequality (2), Δα_(RAi) ^(S) isthe Δα_(R) ^(S) of an arbitrary monomer unit satisfying inequality (2),Δα_(RBi) ^(S) is the Δα_(R) ^(S) of an arbitrary monomer unit notsatisfying inequality (2), and Δα_(GAi) ^(S) and Δα_(GBj) ^(S) inequality (ii) are Δα_(G) ^(S) value obtained by the following equality(II) with respect to an arbitrary monomer unit satisfying inequality (2)and Δα_(G) ^(S) value obtained by the following equality (II) withrespect to an arbitrary monomer unit not satisfying inequality (2),respectively. In other words, Δα_(G) ^(S) is a parameter showingpolarization of a side chain in a monomer unit.Δα_(G) ^(S)=(1/4)(α₂ ^(S)−α₃ ^(S))−(1/8)P(α₁ ^(S)−α₃ ^(S))  (II)

In equality (II), α₁ ^(S), α₂ ^(S), α₃ ⁵ and P are as defined above. Theoptical member comprising the copolymer satisfying the aboveinequalities (3) and (4) is used as a constituent of a liquid crystaldisplay, thereby obtaining a liquid crystal display more diminished inchange of a display color tone.

It is further preferred that the monomer unit not satisfying inequality(2) satisfies the following inequality (5).Δα_(G) ^(S)>3.0×10⁻²⁵ cm³  (5)

Further, it is more preferred that the monomer unit satisfyinginequality (2) satisfies the following inequality (6).Δα_(G) ^(S)<8.5×10⁻²⁵ cm³  (6)

The polymer satisfying inequality (5), more preferably inequality (6),has a particularly preferred O′_(G)(∞), and a liquid crystal displayprovided with the optical member comprising such a polymer as aconstituent is very diminished in change of a display color tone.

In the polymer used in the present invention, a preferred value of thetotal molar fraction X of the monomer unit satisfying inequality (2)(MU 1) varies depending upon the kind of the monomer unit satisfyinginequality (2) (MU 1) and the kind of the monomer unit not satisfyinginequality (2) (MU 2), and ranges preferred from 0.2 to 0.95. When themolar fraction is controlled within such a range, a polymer havingparticularly preferable O′_(R)(∞) and O′_(G)(∞) can be obtained. Thestructure and molar fraction of the monomer unit in the polymer can bedetermined by measuring ¹H-NMR spectra and ¹³C-NMR spectra of thepolymer.

Here, the Δα_(R) ^(S) and Δα_(G) ^(S) are explained.

Both the Δα_(R) ^(S) and the Δα_(G) ^(S) are defined using a main valueof polarizability tensor of a side chain in a monomer unit. In thepresent invention, the side chain of a monomer unit means a portionother than a main chain of a monomer unit defined below.

In the present invention, the main chain in the polymer is defined asfollows. First of all, the polymer is divided into repeating units, ofwhich the polymer is composed. Each repeating unit is called a monomerunit. For example, in the case of a polymer obtained byhomo-polymerization of ethylene, the following thick line portion showsa monomer unit. In general, each monomer unit in a polymer correspondsto each monomer which has been subjected to polymerization forproduction of the polymer.

In the case of ethylene-vinyl acetate copolymer, the following two thickline portions are the two monomer units.

Each monomer unit except for the terminals is usually bonded withanother monomer unit at two positions. In a polymer, there is a verysmall number of terminal monomer units, and therefore, monomer unitsexcept for the terminals are considered in the present invention.

In each of all monomer units except for the terminals in a polymer,there are two atoms involved in a bond with another monomer unit. In thepresent invention, a range of bonds existing, in a monomer unit, betweenthe two atoms involved in the bonds with other monomer units and bondsbetween monomer units is referred to as a main chain.

For example, in the case where in one monomer unit there are two or morekinds of ranges of bonds, like norbornene, connecting the two atomsinvolved in the bonds with other monomer units, the shortest range amongthe ranges of bonds is referred to as a main chain.

Examples of the main chain in various monomer units are as follows. Athick line shows the main chain.

The above formula (a), formula (b) and formula (c) show a propyleneunit, a methyl methacrylate unit and a norbornene unit, respectively.

The polymer used for forming the optical member in accordance with thepresent invention is a polymer whose main chain as defined above iscomposed only of a carbon—carbon single bond.

In the present invention, a portion other than the main chain of apolymer as defined above is defined to be a side chain. Examples of theside chain in various monomer units are as follows. In the followingformulas, bonds between hydrogen and carbon are omitted. The side chainin the present invention includes bonds between hydrogen and carbon inthe side chain and those between hydrogen and carbon in the main chain.

The above formula (a), formula (b) and formula (c) show a propyleneunit, a methyl methacrylate unit and a norbornene unit, respectively.

It is preferred that the polymer used for the optical member accordingto the present invention comprises one or more kinds of monomer unitsbelonging to one of the two kinds of the monomer units (MU 1 and MU 2)differentiated on the basis of Δα_(R) ^(S) defined by equality (I) andone or more kinds of monomer units belonging to the other kind.Δα_(R) ^(S)=α₁ ^(S)−(1/2)(α₂ ^(S)+α₃ ^(S))−(3/4)P(α₁ ^(S)−α₃ ^(S))  (I)

In equality (I), α₁ ^(S), α₂ ^(S) and α₃ ^(S) are each a main value ofpolarizability tensor of side chain in monomer unit and satisfy arelation of α₂ ^(S)≧α₁ ^(S)≧α₃ ^(S), and P is 0 when the monomer unithas a side chain bonding to main chain at two or more positions, or P is1 when the monomer unit has no side chain bonding to main chain at twoor more positions.

The Δα_(G) ^(S) in the present invention is defined by the followingequality (II).Δα_(G) ^(S)=(1/4)(α₂ ^(S)−α₃ ^(S))−(1/8)P(α₁ ^(S)−α₂ ^(S))  (II)

In equality (II), α₁ ^(S), α₂ ^(S) and P are as defined above.

The polarizability tensor of the monomer unit can be determined based onthe kind and direction of chemical bond constituting said monomer unit(see K. G. Denbigh, Trans. Faraday Soc., 36, 936, 1940). The informationcan be surveyed by means of NMR or X-ray diffraction. According to therecent computer simulation, it is possible to calculate these valueswith a considerable accuracy without survey.

In the present invention, in order to make efficient development ofproducts, the polarizability tensor of monomer units was calculatedusing a highly expedient computer simulation software (trade marks of CSChemDraw Pro and CS Chem3D Pro; manufactured by CambridgeSoftCorporation). However, the calculation method is not limited thereto.

The precautions on the calculation of polarizability tensor throughsimulation are to draw a structure in which three monomer units, whosepolarizability tensor is to be calculated, are linked together inseries, and to adopt a bonding direction of the monomer unit centered asthe direction of chemical bond used for the calculation. Thereby, it istaken into consideration that in a real polymer, a monomer unit islinked together in series, so that a bonding angle is influenced bysteric interference of the neighbors. Therefore, as far as this is takeninto consideration, the polarizability tensor may be determined in adifferent manner.

A process for calculation of the polarizability tensor using the CSChemDraw Pro and CS Chem3D Pro is illustrated as follows.

A structure of three monomer units (the polarizability tensor of one ofthe monomer units is to be calculated) linked together in series isdrawn with the CS ChemDraw Pro. The structure is formed into a 3-Dpicture with the CS Chem3D Pro, followed by energy-minimizationoperation. Thereafter, positions of at least all atoms constituting thecentral monomer unit are expressed using the X, Y and Z coordinates. Forall bonds constituting the central monomer unit, the polarizabilitytensor is determined according to, for example, a Denbigh's methoddescribed in Trans. Faraday Soc., 36, 936, 1940.

In the present invention, the total polarizability tensor of the bondsexcept for the main chain of the monomer unit is regarded as thepolarizability tensor of said monomer unit, and respective main valuesof said polarizability tensor are taken as α₁ ^(S), α₂ ^(S) and α₃ ^(S)provided that α₂ ^(S)≧α₁ ^(S)≧α₃ ^(S).

As equality (I) shows, the Δα_(R) ^(S) is a parameter defined by usingmain value of polarizability tensor of the monomer unit and is used asan index for expressing the optical properties of a polymer having saidmonomer unit. As equality (II) shows, the Δα_(G) ^(S) is also aparameter defined by using main value of polarizability tensor of themonomer unit. When used together with the Δα_(R) ^(S), the Δα_(G) ^(S)can serve to express the optical properties of a polymer more clearly.

P in equality (I) is 0, when the concerned monomer unit has a side chainbonding to a main chain at two or more positions, and P is 1, when themonomer unit has no side chain bonding to a main chain at two or morepositions. P is a parameter showing the presence or absence ofrestriction to the side chain in the monomer unit by the main chain.Namely, “P=0” means that the side chain cannot freely rotate on the mainchain, and “P=1” means that the side chain can freely rotate on the mainchain. For example, P is 1 when the monomer unit is styrene,vinylcyclohexane or propylene, and P is zero when the monomer unit isnorbornene or dimethanoocatahydronaphthalene.

The polymer according to the present invention is preferably oneobtained by copolymerizing two or more kinds of monomers. Polymerizationof different kinds of monomers makes it possible to obtain a polymerhaving flexibility and solvent resistance as well as superior opticalproperties and superior heat resistance, and more suitable to be usedfor optical member.

In the case where the polymer used for forming the optical member inaccordance with the present invention is a copolymer obtained bycopolymerizing two or more monomers, it is preferred that the monomerforming the monomer unit satisfying inequality (2) (MU 1) and themonomer forming the monomer unit not satisfying inequality (2) (MU 2)are those selected from the following compounds.

The monomer forming the monomer unit satisfying inequality (2) ispreferably a compound selected from the group consisting of olefinshaving 2 or 3 carbon atoms, norbornene and norbornene derivatives.Examples thereof are ethylene, propylene, norbornene and norbornenederivatives such as 7-methyl-2-norbornene, 7-ethyl-2-norbornene,7-chloro-2-norbornene, 7,7-dimethyl-2-norbornene,7,7-diethyl-2-norbornene, 7-methyl-7-ethyl-2-norbornene,5-methyl-2-norbornene, 5-ethyl-2-norbornene, 5-chloro-2-norbornene,5,6-diethyl-2-norbornene and dimethanooctahydronaphthalene. With respectto these monomers, respective polarizablity tensor main values, α₁ ^(S),α₂ ^(S)and α₃ ^(S), of the side chain of the monomer unit in theirpolymers, and Δα_(R) ^(S) and Δα_(G) ^(S) are as shown below.

TABLE 1 α₁ ^(S) α₂ ^(S) α₃ ^(S) Δ α_(R) ^(S) Δ α_(G) ^(S) Monomer (cm³)(cm³) (cm³) (cm³) (cm³) Ethylene 2.61 × 2.87 × 2.32 × −2.0 × 1.0 × 10⁻²⁴10⁻²⁴ 10⁻²⁴ 10⁻²⁵ 10⁻²⁵ Propylene 4.31 × 5.71 × 3.78 ×   8.8 × 4.4 ×10⁻²⁴ 10⁻²⁴ 10⁻²⁴ 10⁻²⁵ 10⁻²⁵ Norbornene 1.08 × 1.17 × 1.04 × −2.5 × 3.1× 10⁻²³ 10⁻²³ 10⁻²³ 10⁻²⁵ 10⁻²⁵ 7-Methyl-2- 1.28 × 1.39 × 1.20 × −1.2 ×4.8 × norbornene 10⁻²³ 10⁻²³ 10⁻²³ 10⁻²⁵ 10⁻²⁵ 7-Ethyl-2- 1.53 × 1.57 ×1.36 ×   6.1 × 5.2 × norbornene 10⁻²³ 10⁻²³ 10⁻²³ 10⁻²⁵ 10⁻²⁵7-Chloro-2- 1.28 × 1.40 × 1.21 × −2.3 × 4.7 × norbornene 10⁻²³ 10⁻²³10⁻²³ 10⁻²⁵ 10⁻²⁵ 7,7-Dimethyl-2 1.50 × 1.62 × 1.34 ×   2.0 × 7.0 ×norbornene 10⁻²³ 10⁻²³ 10⁻²³ 10⁻²⁵ 10⁻²⁵ 7,7-Diethyl-2- 1.91 × 1.95 ×1.76 ×   5.5 × 4.7 × norbornene 10⁻²³ 10⁻²³ 10⁻²³ 10⁻²⁵ 10⁻²⁵ 7-Methyl-71.73 × 1.77 × 1.54 ×   7.7 × 5.7 × ethyl-2- 10⁻²³ 10⁻²³ 10⁻²³ 10⁻²⁵10⁻²⁵ norbornene 5-Methyl-2- 1.28 × 1.45 × 1.14 × −1.2 × 7.9 ×norbornene 10⁻²³ 10⁻²³ 10⁻²³ 10⁻²⁵ 10⁻²⁵ 5-Ethyl-2- 1.45 × 1.65 × 1.35 ×−4.8 × 7.5 × norbornene 10⁻²³ 10⁻²³ 10⁻²³ 10⁻²⁵ 10⁻²⁵ 5-Chloro-2- 1.24 ×1.44 × 1.21 × −8.5 × 5.7 × norbornene 10⁻²³ 10⁻²³ 10⁻²³ 10⁻²⁵ 10⁻²⁵5,6-Diethyl-2 1.88 × 2.03 × 1.71 ×   5.4 × 7.9 × norbornene 10⁻²³ 10⁻²³10⁻²³ 10⁻²⁵ 10⁻²⁵ Dimethano- 1.75 × 2.01 × 1.67 × −8.9 × 8.3 ×octahydro- 10⁻²³ 10⁻²³ 10⁻²³ 10⁻²⁵ 10⁻²⁵ naphthalene Methyl 1.16 × 1.27× 1.03 × −9.1 × 4.5 × methacrylate 10⁻²³ 10⁻²³ 10⁻²³ 10⁻²⁵ 10⁻²⁵

It is preferred that the monomer unit satisfying inequality (2) furthersatisfies the following inequality (7).−9.5×10⁻²⁵<Δα_(R) ^(S)<9.5×10⁻²⁵ cm³  (7)

As a monomer forming the monomer unit satisfying inequality (7),ethylene, propylene, norbornene and norbornene derivatives can be used.Use of ethylene and/or propylene as the monomer permits production ofpolymer superior in the flexibility and processability. When the polymeris particularly required to have superior heat resistance, it ispreferred to use norbornene or norbornene derivatives. A molar fractionof the monomer unit derived from these monomers is preferably from 0.15to 0.6, and particularly preferably from 0.2 to 0.5.

As a monomer forming the monomer unit not satisfying inequality (2),olefins having 4 or more carbon atoms such as 1-butene, 1-pentene,1-hexene and butadiene, vinylcyclohexane and styrene can be used. Withrespect to these monomers, respective polarizablity tensor main values,α₁ ^(S), α₂ ^(S) and α₃ ^(S), of the side chain of the monomer unit intheir polymers, and Δα_(R) ^(S) and Δα_(G) ^(S) are as shown below.

TABLE 2 α₁ ^(S) α₂ ^(S) α₃ ^(S) Δ α_(R) ^(S) Δ α_(G) ^(S) Monomer (cm³)(cm³) (cm³) (cm³) (cm³) 1-Butene 6.4 × 7.9 × 5.2 × −1.0 × 5.2 × 10⁻²⁴10⁻²⁴ 10⁻²⁴ 10⁻²⁴ 10⁻²⁵ 1-Pentene 8.1 × 1.0 × 6.7 × −1.5 × 7.4 × 10⁻²⁴10⁻²³ 10⁻²⁴ 10⁻²⁴ 10⁻²⁵ 1-Hexene 1.0 × 1.3 × 8.2 × −1.7 × 8.3 × 10⁻²³10⁻²³ 10⁻²⁴ 10⁻²⁴ 10⁻²⁵ Butadiene 6.1 × 7.9 × 4.6 × −1.3 × 6.5 × 10⁻²⁴10⁻²⁴ 10⁻²⁴ 10⁻²⁴ 10⁻²⁵ Vinylcyclo- 1.4 × 1.5 × 1.2 × −1.3 × 6.3 ×hexane 10⁻²³ 10⁻²³ 10⁻²³ 10⁻²⁴ 10⁻²⁵ Styrene 1.4 × 1.5 × 7.6 × −2.4 ×1.2 × 10⁻²³ 10⁻²³ 10⁻²⁴ 10⁻²⁴ 10⁻²⁴

It is preferred that the monomer unit not satisfying inequality (2)satisfies the following inequality (8).−2.5×10⁻²⁴<Δα_(R) ^(S)<−9.5×10⁻²⁵ cm³  (8)

A monomer forming the monomer unit satisfying inequality (8) includescyclic compounds having a vinyl group such as vinylcyclohexane andstyrene. Use of a vinyl group-carrying cyclic compound permitsproduction of a polymer having a high glass transition temperature.

Further, it is more preferred that the monomer forming a monomer unitsatisfying inequality (8) is an aromatic compound having a vinyl groupsuch as styrene, namely, an aromatic vinyl compound. Use of an aromaticvinyl compound permits production of a polymer used for forming anoptical member, which is very hard to cause change in display color tonewhen used for a liquid crystal display. When an aromatic vinyl compoundis used as the monomer forming a monomer unit not satisfying inequality(2), a molar fraction of said monomer unit in the polymer is controlledwithin the range of from 0.1 to 0.4, thereby obtaining a polymer havingpreferable O′_(R)(∞) and O′_(G)(∞).

Further, it is preferred that the monomer forming a monomer unitsatisfying inequality (8) is an aliphatic vinyl compound such asvinylcyclohexane. Use of such an aliphatic vinyl compound permitsproduction of a polymer superior in solvent resistance. In this case, amolar fraction of said monomer unit in the polymer is controlled withinthe range of from 0.3 to 0.8, thereby obtaining a polymer havingpreferable O′_(R)(∞) and O′_(G)(∞).

The polymer constituting the optical member in accordance with thepresent invention may be a homopolymer obtained by polymerizing one kindof monomer, or a copolymer obtained by copolymerizing two or more kindsof monomers. Of these, preferred is a copolymer. With respect to thecopolymer, a polymerization type may be a random type or a block type.The block type copolymer has a defect such that a micro-domain is formeddue to intramolecular phase separation, thereby easily causingscattering of light. Therefore, the random type copolymer is the mostpreferable. A manner of the polymerization is not critical and isexemplified by addition polymerization and condensation polymerization.

The polymer constituting the optical member in accordance with thepresent invention has a glass transition temperature of not lower than110° C. Thereby, the optical member becomes superior in its heatresistance. With respect to a polymer in the optical member used in aliquid crystal display for car use, or a polymer in the optical memberused in combination with a back light having a high luminous fluxdensity, the glass transition temperature (Tg) is preferably not lowerthan 130° C.

As described above, the polymer used for forming the optical member inaccordance with the present invention is preferably a copolymer which isobtained by copolymerizing two or more kinds of monomers and whichcomprises one or more monomer units selected from monomer unitssatisfying inequality (2) (MU 1) and one or more monomer units selectedfrom monomer units not satisfying inequality (2) (MU 2).

Specific examples of a binary copolymer are ethylene/vinylcyclohexanecopolymer, norbornene/styrene copolymer and norbornene/vinylcyclohexanecopolymer.

Specific examples of a ternary copolymer are ethylene/styrene/norbornenecopolymer, ethylene/styrene/dimethanooctahydronaphthalene copolymer,propylene/styrene/norbornene copolymer,propylene/styrene/dimethanooctahydronaphthalene copolymer,ethylene/tert-butoxystyrene/norbornene copolymer,ethylene/vinylcyclohexane/norbornene copolymer,ethylene/vinylcyclohexane/dimethanooctahydronaphthalene copolymer,propylene/vinylcyclohexane/norbornene copolymer andpropylene/vinylcyclohexane/dimethanooctahydronaphthalene copolymer.

Particularly when the optical member is formed using a ternary polymerobtained by using two kinds of monomers, namely, either ethylene orpropylene and either norbornene or a norbornene derivative, as themonomers forming monomer units satisfying inequality (2), and a vinylgroup-containing cyclic compound such as styrene and vinylcyclohexane asthe monomer forming a monomer unit not satisfying inequality (2), suchan optical member can serve to suppress change in display color tone andto improve flexibility and heat resistance when used for the opticalsystems in a liquid crystal display.

With respect to the polymer used for forming the optical product inaccordance with the present invention, polymerization conditions such aspolymerization temperature, polymerization time and, in case ofproduction of a copolymer, feeding amounts of respective monomers can beappropriately varied, thereby controlling a molecular weight, O′_(R)(∞),O′_(G)(∞) and, in case of a copolymer, a copolymerization composition ofthe copolymer, namely, a content proportion of the monomer units. Thepolymerization method is not particularly limited. For example, variousmethods such as a gas phase polymerization method, a bulk polymerizationmethod and a solvent or slurry polymerization method using a suitablesolvent, which are carried out in either a batch manner or a continuousmanner, can be applied. In addition, the polymer can be obtained bypolymerizing the monomer(s) in the presence of a catalyst obtained bycontacting a metallocene catalyst with an aluminum compound or a boroncompound, wherein the metallocene catalyst includesisopropylidene(cyclopentadienyl)(3-tert-butyl-5-methyl-2-phenoxy)titaniumdichloride,dimethylsilylene(tetramethylcyclopentadienyl)(3-tert-butyl-5-methyl-2-phenoxy)titaniumdichloride, ethylenebis(indenyl)zirconium dichloride,dimethylsilylenebis(indenyl)zirconium dichloride,isopropylidenebis(indenyl)zirconium dichloride,dimethylsilylenebis(2-methyl-indenyl)zirconium dichloride,isopropylidenebis(2-methyl-indenyl)-zirconium dichloride andisopropylidene-(cyclopentadienyl) (fluorenyl)zirconium dichloride, thealuminum compound includes triethylaluminum, triisobutylaluminum andmethylalumoxane, and the boron compound includes tri(n-butyl)ammoniumtetrakis-(pentafluorophenyl)borate, N,N-dimethylaniliniumtetrakis(pentafluorophenyl)borate and triphenylmethyltetrakis(pentafluorophenyl)borate. The above-described catalyst systemmay be incorporated with a third component such as molecular oxygen, analcohol, an ether, a peroxide, a carboxylic acid, an acid anhydride, anacid chloride, an ester, a ketone, a nitrogen-containing compound, asulfur-containing compound, a halogen-containing compound, moleculariodine and other Lewis acids. The polymerization using said catalystsystem can be carried out in the presence or absence of a solventusually under the conditions of polymerization temperature of from −50to 100° C. and polymerization pressure of from 0 to 50 kg/cm².

The polymer used for forming the optical member in accordance with thepresent invention can be appropriately blended with ultravioletabsorbers, antioxidants, lubricants, anti-static agents, antimicrobialagents, anti-fogging agents and plastisizers in a manner such thateffects of the present invention are not remarkably impaired. Examplesof the antioxidants usable are6-[3-(3-methyl-4-hydroxy-5-tert-butylphenyl)propoxy]-2,4,8,10-tetra-tert-butyl-dibenz[d,f][1,3,2]dioxaphosphepin (commercial name: Sumilizer (registeredtrademark) GP, manufactured by Sumitomo Chemical Co., Ltd.),2,6-di-tert-butyl-4-methylphenol (commercial name: Sumilizer (registeredtrademark) BHT-R, manufactured by Sumitomo Chemical Co., Ltd.),octadecyl-3-(3,5-di-tert-butyl-4-hydroxyphenol)propionate (commercialname: Sumilizer (registered trademark) BP-76, manufactured by SumitomoChemical Co., Ltd.),pentaerythrityltetrakis[3-(5-di-tert-butyl-4-hydroxyphenol)-propionate](commercial name: Sumilizer. (registered trademark) BP-101, manufacturedby Sumitomo Chemical Co., Ltd.) andtris(2,4-di-tert-butylphenyl)-phosphite (commercial name: Sumilizer(registered trademark) P-16, manufactured by Sumitomo Chemical Co.,Ltd.).

The optical member in accordance with the present invention is high inits heat resistance and transparency and superior in its properties topolarization, and therefore suitable for lenses such as lenses foreyeglasses, f·θ lenses and pick up lenses, prisms, optical fibers, disksubstrates for an optical recording medium or a magneto-opticalrecording medium, and a constituent of optical systems in a liquidcrystal display. It is particularly suitable as a protecting film of apolarizing plate.

The optical member in accordance with the present invention, whichincludes constituents of a liquid crystal display typified by a carryingplate, a polarizing plate, a protecting film of a polarizing plate, asubstrate of liquid crystal cells, a light diffusion plate and acondensing film, can be formed according to a forming method such asinjection molding, extrusion forming, rolling and press molding. Aforming method for forming the polymer used for the optical member inaccordance with the present invention into a film such as a polarizingplate-protecting film and a film for liquid crystal cell substrates or asheet is exemplified by T die cast forming, extrusion forming such astubular film process, rolling such as calendering, press molding andsolvent casting. When the polymer used for the optical member inaccordance with the present invention is processed into an optical film,it is usually processed so as to have a thickness of from 50 to 300 μm.

It is preferable to form the polarizing plate by laminating thepolarizing plate-protecting film in accordance with the presentinvention on one or both sides of the polarizing film. Materials of thepolarizing film are not particularly limited. Usually, polyvinyl alcoholresins are used. How to bond the polarizing film and the polarizingplate-protecting film with each other is not particularly limited, andusually an adhesive is used. As the adhesive, for examples, urethaneadhesives, acrylic adhesives, chlorinated polyolefin adhesives, etheradhesives, ester adhesives and polyethyleneimine adhesives arepreferably used.

The polarizing plate in accordance with the present invention can bepreferably used in combination with a phase difference film, a liquidcrystal cell and a gas barrier layer to constitute a liquid crystaldisplay.

The lenses for eyeglasses can be formed according to a castpolymerization method (Fumio Ide, “KOKO MADE KITA TOMEI JUSHI(Transparent Resin Improved Thus)”, page 211, issued by Kogyo ChosakaiPublishing Co., Ltd. (2001)).

Various lenses including pick up lenses, and prisms can be formed, forexample, by injection molding (Fumio Ide, “KOKO MADE KITA TOMEI JUSHI(Transparent Resin Improved Thus)”, page 97, issued by Kogyo ChosakaiPublishing Co., Ltd. (2001)).

Optical fibers can be formed, for example, through spinning for theformation of fiber (original yarn), drafting and cable processing (FumioIde, “KOKO MADE KITA TOMEI JUSHI (Transparent Resin Improved Thus)”,page 149, issued by Kogyo Chosakai Publishing Co., Ltd. (2001)).

The disk substrates for an optical recording medium or a magneto-opticalrecording medium can be formed, for example, by injection press molding(Fumio Ide, “KOKO MADE KITA TOMET JUSHI (Transparent Resin ImprovedThus)”, page 122, issued by Kogyo Chosakai Publishing Co., Ltd. (2001)).

EXAMPLES

The present invention is explained in more detail with reference toExamples as follows, but the present invention is not limited thereto.

(1) Glass Transition Temperature (Tg)

The glass transition temperature (Tg) of a polymer was measuredaccording to JIS K7121 with use of a differential scanning calorimeterDSC 220, manufactured by Seiko Instruments Inc.

(2) O′_(R)(∞) and O′_(G)(∞)

The O′_(R)(∞) and O′_(G)(∞) were determined according to a rule ofcorrected stress optics (T. Inoue et al. “Polymer”, 38, 1215, 1997; T.Inoue et al. “Rheologica Acta”, 36, 239, 1997; T. Inoue et al.“Macromolecules”, 29, 6240, 1996; T. Inoue et al. “Macromolecules”, 24,5670, 1991; and T. Inoue et al. “KOBUNSHI RONBUN-SHU (Collection ofPapers on High Molecules)”, 53, 602, 1996). In measuring, a commerciallyavailable viscoelasticity measurement apparatus equipped with an opticalsystem for the measurement of double refraction was used. As a samplefor the measurement, a press sheet having a thickness of 500 μm wasused.

Vibration distortion periodically varying with the lapse of time wasapplied to the polymer, and the generated changes in stress and doublerefraction were simultaneously measured. From the results obtained,C_(R), C_(G), E′_(R)(∞) and E′_(G)(∞) were determined according to therule of corrected stress optics, and the obtained values weresubstituted for the equalities (e) and (f), thereby determining theO′_(R)(∞) and O′_(G)(∞)O′ _(R)(∞)=C _(R) E′ _(R)(∞)  (e)O′ _(G)(∞)=C _(G) E′ _(G)(∞)  (f)(3) Δα_(R) ^(S) and Δα_(G) ^(S) of monomer Unit

A structure of three monomer units (the Δα_(R) ^(S) and Δα_(G) ^(S) ofone of the monomer units is to be calculated) linked together in serieswas drawn with the CS ChemDraw Pro. The structure was formed into a 3-Dpicture with the CS Chem3D Pro, followed by energy-minimizationoperation. Thereafter, all atom positions were shown using the X, Y andZ coordinates. With respect to each of the bonds other than the mainchain constituting the central monomer unit, the polarizability tensorswere determined, and the sum of the tensors was regarded as thepolarizability tensor of said monomer unit. Then their main values, α₁^(S), α₂ ^(S) and α₃ ^(S) (provided that α₂ ^(S)≧α₁ ^(S)≧α₃ ^(S)) weredetermined. Using the resulting main values, Δα_(R) ^(S) and Δα_(G) ^(S)were calculated from equality (I) and equality (II), respectively.Δα_(R) ^(S)=α₁ ^(S)−(1/2)(α₂ ^(S)+α₃ ^(S))−(3/4)P(α₁ ^(S)−α₃ ^(S))  (I)Δα_(G) ^(S)=(1/4)(α₂ ^(S)−α₃ ^(S))−(1/8)P(α₁ ^(S)−α₃ ^(S))  (II)wherein P=0 or 1.(4) Monomer Unit Content

The contents (molar fractions, X and Y) of the monomer unit satisfyinginequality (2) and the monomer unit not satisfying inequality (2) in thepolymer used for the optical member were determined from ¹H-NMR and¹³C-NMR spectra, respectively.

The ¹H-NMR spectra were measured at room temperature using a nuclearmagnetic resonance apparatus, JNM-EX270, manufactured by JEOL Ltd., andusing dichloromethane-d₂ as a solvent.

The ¹³C-NMR spectra were measured at 135° C. using a nuclear magneticresonance apparatus, AC-250, manufactured by the Bruker Companies, andusing o-dichlorobenzene/o-dichlorobenzene-d₄ (volume ratio=4/1) as asolvent.

(5) Δα_(R) ^(P) and Δα_(G) ^(P)

The Δα_(R) ^(S) and Δα_(G) ^(S) of the monomer unit satisfyinginequality (2) and the Δα_(R) ^(S) and Δα_(G) ^(S) of the monomer unitnot satisfying inequality (2) are taken as Δα_(RAi) ^(S) and Δα_(GAi)^(S), and Δα_(RBi) ^(S) and Δα_(GBi) ^(S), respectively. Using theΔα_(R) ^(S), Δα_(G) ^(S) and molar fractions X and Y for each monomerunit obtained above, Δα_(R) ^(P) and Δα_(G) ^(P) were calculated fromequality (i) and equality (ii), respectively. $\begin{matrix}{{\Delta\quad\alpha_{R}^{P}} = {{\sum\limits_{i = 1}^{m}\left( {X_{i}\Delta\quad\alpha_{RAi}^{S}} \right)} + {\sum\limits_{j = 1}^{n}\left( {Y_{j}\Delta\quad\alpha_{RBj}^{S}} \right)}}} & (i) \\{{\Delta\quad\alpha_{G}^{P}} = {{\sum\limits_{i = 1}^{m}\left( {X_{i}\Delta\quad\alpha_{GAi}^{S}} \right)} + {\sum\limits_{j = 1}^{n}\left( {Y_{j}\Delta\quad\alpha_{GBj}^{S}} \right)}}} & ({ii})\end{matrix}$(6) Change in Color Tone

A polymer film obtained by press molding was bonded to both sides of apolarizing film of polyvinyl alcohol formed according to a conventionalprocess using an urethane adhesive, thereby obtaining a laminate film.Successively, the laminate film (polarizing plate) was cut into a pieceof 130 mm square so that one of the side lines of the piece forms anangle of 45° to the absorption axis of the laminate film. Using anacrylic adhesive, the piece of laminate films were bonded to both sidesof a transparent glass plate so as to form a cross Nicol, therebyobtaining a laminate product. The laminate product was allowed to standfor 500 hours at 80° C. A color tone of the laminate product before andafter said treatment was observed (the presence or absence of lightleakage when the laminate product was placed on a light box), therebyexamining change in color tone.

Example 1

In a 400 ml autoclave purged with argon, 57 ml of styrene, 100 ml of atoluene solution of norbornene (5 mol/l) and 73 ml of dewatered toluenewere introduced, and thereafter ethylene was fed to reach 0.4 MPa. Tothe mixture, 4 ml of a toluene solution of triisobutylaluminum (1 mol/l,manufactured by TOSOH AKZO Co.), a solution prepared by dissolving 10.8mg ofisopropylidene(cyclopentadienyl)(3-tert-butyl-5-methyl-2-phenoxy)titaniumdichloride in 5.4 ml of dewatered toluene, and a mixture of 39.8 mg ofN,N-dimethylanilinium tetrakis(pentafluorophenyl)borate and 10 ml ofdewatered toluene were added in order, and the resulting reaction liquidwas stirred for 3 hours at 50° C. Thereafter, the reaction liquid waspoured into a mixture of 5 ml of hydrochloric acid (12 N) and 800 ml ofacetone, and the precipitated white solid was separated by filtration.The solid was washed with acetone, and thereafter dried under reducedpressure, thereby obtaining 17.14 g of a polymer. The copolymerizationcomposition of styrene and that of norbornene in the polymer were foundto be 23 mol % and 41 mol %, respectively. Based on the fact that anyendothermic peak owing to crystal melting was not observed in the DSCmeasurement, the polymer was confirmed to be amorphous. The polymer waspress-molded at 270° C. to obtain a sheet of 500 μm thickness in a stripform, and the O′_(R)(∞) and O′_(G)(∞) of the sheet were determined inthe foregoing manner. Further, the obtained polymer was subjected topress molding in a manner similar to that described above, therebyobtaining an optical film of 135 μm thickness. As a result of a test forchange in color tone, the whole of the laminate product was observed tobe uniformly black before and after the 80° C. treatment. Thus, therewas observed almost no change in color tone by said treatment. Even whena liquid crystal display provided with said film as a polarizingplate-protecting film is employed for a long period of time, change indisplay color tone will be very little.

Example 2

In a 400 ml autoclave purged with argon, 17 ml of styrene, 60 ml of atoluene solution of norbornene (5 mol/l) and 54 ml of dewatered toluenewere introduced, and thereafter ethylene was fed to reach 0.4 MPa. Tothe mixture, 4 ml of a toluene solution of triisobutylaluminum (1 mol/l,manufactured by TOSOH AKZO Co.), a solution prepared by dissolving 8.7mg ofisopropylidene(cyclopentadienyl)(3-tert-butyl-5-methyl-2-phenoxy)titaniumdichloride in 4.3 ml of dewatered toluene, and a mixture of 31.5 mg ofN,N-dimethylanilinium tetrakis(pentafluorophenyl)borate and 10 ml ofdewatered toluene were added in order, and the resulting reaction liquidwas stirred for 1 hour at 50° C. Thereafter, the reaction liquid waspoured into a mixture of 5 ml of hydrochloric acid (12 N) and 800 ml ofacetone, and the precipitated white solid was separated by filtration.The solid was washed with acetone, and thereafter dried under reducedpressure, thereby obtaining 8.31 g of a polymer. A copolymerizationcomposition of styrene in the polymer and the copolymerizationcomposition of norbornene were found to be 16 mol % and 43 mol %,respectively. Based on the fact that any endothermic peak owing tocrystal melting was not observed according to DSC measurement, thepolymer was confirmed to be amorphous. The polymer was press-molded at270° C. to obtain a sheet of 500 μm thickness in a strip form, and theO′_(R)(∞) and O′_(G)(∞) of the sheet were determined in the foregoingmanner. Further, the obtained polymer was subjected to press molding ina manner similar to that described above, thereby obtaining an opticalfilm of 135 μm thickness. As a result of a test for change in colortone, the whole of the laminate product was observed to be uniform blackbefore and after the 80° C. treatment. Thus, there was not excessivelyobserved change in the color tone by said treatment. Even when a liquidcrystal display provided with said film as a polarizing plate-protectingfilm is employed for a long period of time, change in display color tonewill be little.

Example 3

In a 1.5 m³ autoclave purged with argon, 75 kg of styrene, 143 kg of atoluene solution of norbornene (5 mol/l) and 113 kg of dewatered toluenewere introduced, and thereafter ethylene was fed to reach 0.4 MPa. Tothe mixture, 6.9 kg of a toluene solution of triisobutylaluminum (1mol/l, manufactured by TOSOH AKZO Co.), a solution prepared bydissolving 12 g ofisopropylidene(cyclopentadienyl)(3-tert-butyl-5-methyl-2-phenoxy)titaniumdichloride in 2.8 kg of dewatered toluene, and a mixture of 51 g ofN,N-dimethylanilinium tetrakis(pentafluorophenyl)borate and 8.7 kg ofdewatered toluene were added in order, and the resulting reaction liquidwas stirred for 3.8 hours at 50° C. Thereafter, the reaction liquid waspoured into a mixture of 2 liters of hydrochloric acid (12 N) and 3600liters of acetone, and the precipitated white solid was separated byfiltration. The solid was washed with acetone, and thereafter driedunder reduced pressure, thereby obtaining 34 kg of a polymer. Acopolymerization composition of styrene and that of norbornene in thepolymer were found to be 21 mol % and 42 mol %, respectively. Based onthe fact that any endothermic peak owing to crystal melting was notobserved according to DSC measurement, the polymer was confirmed to beamorphous. The polymer was press-molded at 270° C. to obtain a sheet of500 μm thickness in a strip form, and the O′_(R)(∞) and O′_(G)(∞) of thesheet were determined in the foregoing manner. Further, the obtainedpolymer was subjected to press molding in a manner similar to thatdescribed above, thereby obtaining an optical film of 135 μm thickness.As a result of a test for change in color tone, the whole of thelaminate product was observed to be uniformly black before and after the80° C. treatment. Thus, there was not observed any remarkable change incolor tone by said treatment. Even when a liquid crystal displayprovided with said film as a polarizing plate-protecting film isemployed for a long period of time, change in display color tone will bevery little.

Comparative Example 1

Using the film formed from the amorphous polymer obtained bypolymerizing the monomer as shown in a column of Comparative Example 1in Table 4, a test for change in color tone was carried out. Before the80° C. treatment, the whole of the laminate product was observed to beuniformly black. Whereas, after the treatment, there was observed lightleakage (white discharging) in the neighborhood of the center in eachside of the laminate product. When a liquid crystal display providedwith said film as a polarizing plate-protecting film is employed for along period of time, change in display color tone will becomeremarkable, so that it becomes hard to handle the display.

Comparative Example 2

Using the film formed from the amorphous polymer obtained bypolymerizing the monomer as shown in a column of Comparative Example 2in Table 4, a test for change in color tone was carried out. Before the80° C. treatment, the whole of the laminate product was observed to beuniformly black. Whereas, after the treatment, there was observed lightleakage (white discharging) in the neighborhood of the center in eachside of the laminate product. When a liquid crystal display providedwith said film as a polarizing plate-protecting film is employed for along period of time, change in display color tone will becomeremarkable, so that it becomes hard to handle the display.

Comparative Example 3

Using the film formed from the amorphous polymer obtained bypolymerizing the monomers as shown in a column of Comparative Example 3in Table 4, a test for change in color tone was carried out. Before the80° C. treatment, the whole of the laminate product was observed to beuniformly black. Whereas, after the treatment, there was observed lightleakage (white discharging) in the neighborhood of the center in eachside of the laminate product. When a liquid crystal display providedwith said film as a polarizing plate-protecting film is employed for along period of time, change in display color tone will becomeremarkable, so that it becomes hard to use the display.

Comparative Example 4

Using the film formed from the amorphous polymer obtained bypolymerizing the monomers as shown in a column of Comparative Example 4in Table 4, a test for change in color tone was carried out. Before the80° C. treatment, the whole of the laminate product was observed to beuniformly black. Whereas, after the treatment, there was observed lightleakage (white discharging) in the neighborhood of the center in eachside of the laminate product. When a liquid crystal display providedwith said film as a polarizing plate-protecting film is employed for along period of time, change in display color tone will becomeremarkable, so that it becomes hard to use the display.

Comparative Example 5

In a 400 ml autoclave purged with argon, 11.4 ml of styrene, 20 ml of atoluene solution of norbornene (5 mol/l) and 105 ml of dewatered toluenewere introduced in advance, and thereafter ethylene was fed to reach 0.8MPa. A solution prepared by dissolving 15.5 mg ofisopropylidene-(cyclopentadienyl)(3-tert-butyl-5-methyl-2-phenoxy)titaniumdichloride in 15 ml of dewatered toluene and 2.5 ml of a toluenesolution of triisobutylaluminum (1 mol/l, manufactured by TOSOH AKZOCo.) was mixed and added thereto. Successively a solution prepared bydissolving 80.1 mg of N,N-dimethylaniliniumtetrakis(pentafluorophenyl)borate in 47 ml of dewatered toluene wasadded thereto. The resulting reaction liquid was stirred for 1 hour at60° C. Thereafter, the reaction liquid was poured into a mixture of 5 mlof hydrochloric acid (12 N) and 1000 ml of acetone, and the precipitatedwhite solid was separated by filtration. The solid was washed withacetone, and thereafter dried under reduced pressure, thereby obtaining26.85 g of a polymer. A copolymerization composition of styrene and thatof norbornene in the polymer were found to be 16 mol % and 15 mol %,respectively. Based on the fact that any endothermic peak owing tocrystal melting was not observed according to DSC measurement, thepolymer was confirmed to be amorphous. The polymer was press-molded at190° C. to obtain a sheet of 500 μm thickness in a strip form, and theO′_(R)(∞) and O′_(G)(∞) of the sheet were determined in the foregoingmanner. Further, the obtained polymer was subjected to press molding ina manner similar to that described above, thereby obtaining an opticalfilm of 135 μm thickness. Using the resulting film, a test for change incolor tone was carried out. Before the 80° C. treatment, the whole ofthe laminate product was observed to be uniformly black. Whereas, afterthe treatment, there was observed light leakage (white discharging) inthe neighborhood of the center in each side of the laminate product.When a liquid crystal display provided with said film as a polarizingplate-protecting film is employed for a long period of time, change indisplay color tone will become remarkable, so that it becomes hard touse the display.

With respect to each polymer obtained in the above Examples 1 to 3 andComparative Examples 1 to 5, Δα_(R) ^(S) and Δα_(G) ^(S) of each monomerunit constituting the polymer, the molar ratio of each monomer unit inthe polymer, O′_(R)(∞), O′_(G)(∞) and the glass transition temperatureof the polymer and the result of change in color tone of the polarizingplate formed using the polymer are summarized in Table 3, Table 4, FIG.1 and FIG. 2. The change in color tone of each sample (laminate product)examined according to the foregoing test method was expressed based onthe following criteria (1) to (5).

-   -   (1): Almost no change in color tone is observed.    -   (2): Change in color tone is observed to be more intense        than (1) but less intense than (3).    -   (3): Slight change in color tone is observed, but the degree of        change in color tome is not problematic from a practical point        of view.    -   (4): Change in color tone is observed to be more intense        than (3) but less intense than (5).    -   (5): Considerable change in color tone is observed.

TABLE 3 Δα_(R) ^(S) Δα_(G) ^(S) Change Monomer unit ()′_(R)(∞) O′_(G)(∞)Δα_(R) ^(S) Δα_(G) ^(S) (10⁻²⁵ (10⁻²⁵ in color Name Structure (x10²)(x10²) (10⁻²⁵ cm³) (10⁻²⁵ cm³) Mol % cm³) cm³) Tg (° C.) tone Example 1Ethylene (MU1)

−1.2 −0.37 −2.0 1.0 36 −7.3 4.4 133 (2) Norbornene (MU1)

−2.5 3.1 41 Styrene (MU2)

−23.9 12.0 23 Example 2 Ethylene (MU1)

−0.22 −1.1 −2.0 1.0 41 −5.7 3.6 140 (3) Norbornene (MU1)

−2.5 3.1 43 Styrene (MU2)

−23.9 12.0 16 Example 3 Ethylene (MU1)

−0.60 −0.52 −2.0 1.0 37 −6.8 4.2 133 (1) Norbornene (MU1)

−2.5 3.1 42 Styurene (MU2)

−23.9 12.0 21

TABLE 4 Change Δα_(R) ^(S) Δα_(G) ^(S) in O′_(R) (∞) O′_(G) (∞) Δα_(R)^(S) Δα_(G) ^(S) (10⁻²⁵ (10⁻²⁵ Tg color Monomer unit (x10²) (x10²)(10⁻²⁵ cm³) (10⁻²⁵ cm³) Mol % cm³) cm³) (° C.) tone Com. Ex. 1Dimethanoocta- hydronaphthalene (MU1)

2.9 −1.9 −8.9 8.3 100 −8.9 8.3 142 (5) Com. Ex. 2 6-Methyl-6-methoxycarbonyl- 1,4,5,8- dimethano- 1,4,4a,5,6,7,8,8a- octahydro-naphthalene (MU2)

2.2 −1.1 −12.1 10.4 100 −12.1 10.4 140 (5) Com. Ex. 3 Ethylene (MU1)

1.1 −1.1 −2.0 1.0 — — — 141 (5) Dimethanoocta- hydronaphthalene (MU1)

−6.8 4.2 — Com. Ex. 4 Ethylene (MU1)

1.5 −2.1 −2.0 1.0 — — — 140 (5) Norbornene (MU1)

−2.5 3.1 — Com. Ex. 5 Ethylene (MU1)

−0.20 2.1 −2.0 1.0 69 −5.6 3.1 35 (5) Norbornene (MU1)

−2.5 3.1 15 Styrene (MU2)

−23.9 12.0 16

INDUSTRIAL APPLICABILITY

The optical member in accordance with the present invention is superiorin its heat resistance and transparency and high in its stability ofoptical properties. Therefore, the optical member can be used as, forexample, a constituent of optical systems in a liquid crystal display,thereby suppressing change in display color tone depending on variationof using circumstances of the liquid crystal display.

1. An optical member comprising a polymer which is amorphous and has aglass transition temperature of not lower than 110° C. and opticalproperty parameters O′_(R)(∞) and O′_(G)(∞) that satisfy the followinginequality (1),|O′ _(G)(∞)|<−0.75×|O′ _(R)(∞)|+0.017  (1).
 2. The optical memberaccording to claim 1, wherein the polymer comprises a copolymercomprising an m kind of monomer unit satisfying the following inequality(2), wherein m is an integer of not less than 1, and an n kind ofmonomer unit not satisfying the following inequality (2), wherein n isan integer of not less than 1, and satisfying the following inequalities(3) and (4),−9.5×10⁻²⁵ cm³<Δα_(R) ^(S)  (2)−1.0×10⁻²⁴<Δα_(R) ^(P)<−5.0×10⁻²⁵ cm³  (3)3.4×10⁻²⁵<Δα_(G) ^(P)<5.4×10⁻²⁵ cm³  (4) wherein, in inequality (2),Δα_(R) ^(S) is a parameter defined by the following equality (I),Δα_(R) ^(S)=α₁ ^(S)−(1/2)(α₂ ^(S)+α₃ ^(S))−(3/4)P(α₁ ^(S)−α₃ ^(S))wherein, in equality (I), α₁ ^(S), α₂ ^(S) and α₃ ^(S) are each a mainvalue of polarizability tensor of a side chain in a monomer unit andsatisfy a relation of α₂ ^(S)≧α₁ ^(S)≧α₃ ^(S), and P is 0 when themonomer unit has a side chain bonding to main chain at two or morepositions, or P is 1 when the monomer unit has no side chain bonding tomain chain at two or more positions, and wherein, in inequalities (3)and (4), Δα_(R) ^(P) and Δα_(G) ^(P) are parameters defined by thefollowing equalities (i) and (ii), respectively, $\begin{matrix}{{\Delta\quad\alpha_{R}^{P}} = {{\sum\limits_{i = 1}^{m}\left( {X_{i}\Delta\quad\alpha_{RAi}^{S}} \right)} + {\sum\limits_{j = 1}^{n}\left( {Y_{j}\Delta\quad\alpha_{RBj}^{S}} \right)}}} & (i) \\{{\Delta\quad\alpha_{G}^{P}} = {{\sum\limits_{i = 1}^{m}\left( {X_{i}\Delta\quad\alpha_{GAi}^{S}} \right)} + {\sum\limits_{j = 1}^{n}\left( {Y_{j}\Delta\quad\alpha_{GBj}^{S}} \right)}}} & ({ii})\end{matrix}$ wherein, in equalities (i) and (ii), X_(i) is a molarfraction of an arbitrary monomer unit satisfying inequality (2), Y_(j)is a molar fraction of an arbitrary monomer unit not satisfyinginequality (2), Δα_(RAi) ^(S) is Δα_(R) ^(S) of an arbitrary monomerunit satisfying inequality (2), Δα_(RBi) ^(S) is Δα_(R) ^(S) of anarbitrary monomer unit not satisfying inequality (2), and, in equality(ii), Δα_(GAi) ^(S) and Δα_(GBi) ^(S) are Δα_(G) ^(S) value defined bythe following equality (II) with respect to an arbitrary monomer unitsatisfying inequality (2) and Δα_(G) ^(S) value defined by the followingequality (II) with respect to an arbitrary monomer unit not satisfyinginequality (2), respectively,Δα_(G) ^(S)=(1/4)(α₂ ^(S)−α₃ ^(S))−(1/8)P(α₁ ^(S)−α₃ ^(S))  (II)wherein, in equality (II), α₁ ^(S), α₂ ^(S), α₃ ^(S) and P are asdefined above.
 3. The optical member according to claim 2, wherein thecopolymer comprises a monomer unit derived from a compound selected fromthe group consisting of olefins having 2 or 3 carbon atoms, norborneneand norbornene derivatives as the monomer unit satisfying inequality(2), and a monomer unit derived from a vinyl group-containing cycliccompound as the monomer unit not satisfying inequality (2).
 4. Theoptical member according to claim 3, wherein the copolymer comprises amonomer unit derived from an aromatic vinyl compound as the monomer unitnot satisfying inequality (2).
 5. The optical member according to claim4, wherein the copolymer has a total molar fraction of the monomer unitnot satisfying inequality (2) ranging from 0.1 to 0.4 inclusive.
 6. Theoptical member according to claim 3, wherein the copolymer comprises amonomer unit derived from an alicyclic vinyl compound as the monomerunit not satisfying inequality (2).
 7. The optical member according toclaim 6, wherein the copolymer has a total molar fraction of the monomerunit not satisfying inequality (2) ranging from 0.3 to 0.8 inclusive. 8.The optical member according to any one of claims 1 to 7, which is apolarizing plate-protecting film.
 9. The optical member according to anyone of claims 1 to 7, which is a substrate for liquid crystal cells. 10.A polarizing plate, wherein the optical member according to any one ofclaims 1 to 7, which is a polarizing plate-protecting film, is mountedon at least one side surface of a polarizing film.
 11. A liquid crystaldisplay, which is provided with a substrate for liquid crystal cellsaccording to a polarizing plate according to claim
 10. 12. A liquidcrystal display, which is provided with a polarizing plate according toclaim 10.